A little confused. Do "snapshots" (vs dump=image) have any correlation, non-unix?

I made a snapshot, it was "2.9G" but only actually
a few MB; then the dump was 503M. I've long
known about dumps, but the snapshot is
actually== ? in windows or "boot utility" terminology,
if an equivalent exists ??
..............
(Not an urgent question) afaik.